Oligonucleotide hybridization electrochemical detection

Fig. 6. (A) The electrochemical detection of hybridization on Au electrode surface. Probe oligonucleotides with 5 -thiol are incubated on the Au surface for 12h. Strong covalent bond between thiols and Au surface results in the formation of the probe-modified electrode (A1), noncomplementary oligonucleotides are incubated with the probe-modified electrode (A2) however, no hybridization takes place between these two strands (A3), the redox label, Hoechst 33258, is incubated with the probe-modified-electrode (A4), since the redox label cannot intercalate with the single-strand probe oligonucleotides on the surface, a small electrochemical current response is obtained (A5). The current intensity at the peak potential (-0.6V) is recorded relative to the background response of the blank buffer solution (dashed grey line). (B) The electrochemical detection of hybridization on Au electrode surface. Probe oligonucleotides with 5 -thiol are incubated on the Au surface for -12 h for the preparation of the probe-modified electrode (B1), target oligonucleotides are...

Pham M. C., Piro B., Tran L. D., Ledoan T., and Dao L. H., Direct electrochemical detection of oligonucleotide hybridization on poly(5-hydroxy-l,4-naphthoquinone-co-5-hydroxy-3-thioacetic acid-l,4-naphthoquinone) film, Anal Chem., 75(23), 6748-6752, 2003. 

An alternative approach used the same sensor electrode, but DNA hybridization was detected by electrochemical impedance spectroscopy (EIS), which eliminates the necessity of applying a redox-labeled reporter oligonucleotide (Kafka et al., 2008). The ferri-/ferrocyanide system was used as a redox probe instead. DNA immobilized on the gold electrode affected the electrochemical conversion of the negatively charged ferri- and ferrocyanide ions, as depicted in Figure 4.2. 

G.-U. Flechsig and T. Reske, Electrochemical detection of DNA hybridization by means of osmium tetroxide complexes and protective oligonucleotides, Ann/. Chem. 79(5), 2125-2130 (2007). 

An electrogenerated copolymer 133 of 3-methylthiophene and 3-thiopheneacetic acid has been developed for covalent attachment of lactate oxidase [247]. Polymer 134 with an activated ester was functionalized with an oligonucleotide probe for the electrochemical detection of DNA hybridization [248]. 

There are a variety of methods to detect the DNA content of food, which can be used to unequivocally identify the nature of the product [4]. Among the various systems for nucleic acid detection, electrochemical DNA analysis can involve direct detection based on a guanine signal (label-free) [5] or an electrocatalytic mechanism (label-based). Quantum dots (QDs) [6,7], metal nanoparticles (NPs) [8,9], enzymes [10,11], and metal complexes [12, 13] can be employed as labels. This chapter focuses on electrochemical biosensing systems based on DNA hybridization events, which offer novel routes for food safety and security applications. Particularly, it describes in detail different approaches reported in the latest years on the immobilization of oligonucleotides on electrochemical transducers for sensing of various compounds with interest in food industry. In addition, some interesting applications in other fields that can easily be extended to that of food are also included. 

Nunes Kirchner, C., Szunerits, S., Wittstock, G. Scanning electrochemical microscopy (SECM) based detection of oligonucleotide hybridization and simultaneous determination of the surface concentration of immobilized oligonucleotides on gold. Electroanalysis 2(X)7, 19, 1258-1267. 

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